Trying to create a regression test for #20261

Hi, As a intermediate beginner in Haskell, I want to try to tackle a small issue for contributing to GHC. I've looked into https://gitlab.haskell.org/ghc/ghc/-/issues/20261, but it's not clear how to integrate a running time in a regression test.

From what I understand, regression tests should be compared against sucess/failure or a given output. Should there be a hard-coded limit ? If that's the case, how could I create such a test ? I could not find a similar test in the source code.

Any help is appreciated, thanks ! -- Alexis Praga